1. Field of the Invention
This invention relates to systems to provide environmental cooling in vehicle cabins, particularly in automobile cabins.
2. Description of the Related Art
Environmental heating and cooling systems for the vehicle cabins are employed for most types of vehicles in order to maintain the occupant comfort. Such systems are particularly important in vehicles which are used to transport people through extreme weather and environmental conditions such as aircraft or automobiles. Cooling systems are typically more complex than heating systems.
In automobile applications, main stream systems employ a vapor compression cycle using freon R134a, etc. as the working fluid in a closed system. In the well known system, freon is pressurized by a compressor undergoing a phase change to liquid and rise in temperature. The compressor is typically a centrifugal, vane, or scroll type pump that increases the pressure and temperature of the freon. The heated liquid freon is then passed through an intercooler (typically disposed at the front of the vehicle such that cold air can cool the liquid freon. The cooled liquid freon is then passed through an expansion device which allows the liquid freon to return to gaseous state rapidly cooling in the process. The cooled gaseous freon is then passed through another intercooler which is coupled to the cabin air forced by a fan in order to cool it, heating the gaseous freon in the process. The heated gaseous freon is then returned to the compressor to begin the cycle again.
On the other hand, aircraft cabin cooling typically employ an air cycle machine using a standard open cycle reverse Brayton process. The air cycle cooling process uses air instead of a phase changing fluid such as Freon in the gas cycle. Bladed turbines are used both for compressing the incoming air and expanding it after the heated compressed air has been cooled. Accordingly, no condensation or evaporation of a refrigerant is involved. In addition, in this case, the cooled air output from the process is used directly in the cabin or for cooling electronic equipment.
Typical automobile environmental cooling systems are efficient but expensive due to their use of refrigerant. In addition, the compressors are expensive to manufacture and the overall system is complex and susceptible to failure if a seal is breached anywhere. Typical aircraft cabin cooling systems employ expensive bladed turbines in order to compress and expand air in the system.
In view of the foregoing, there is a need in the art for improved apparatuses and methods for cooling cabin environments in automobiles. There is particularly a need for such apparatuses and methods to operate efficiently and reliably. Further, there is a need for such apparatuses and methods to be simple and affordable to manufacture and maintain and operate without refrigerant. These and other needs are met by embodiments of the present invention as detailed hereafter.